1. Field of the invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus for coordinating inter-cell interference in a wireless communication system.
2. Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) is an improved version of a universal mobile telecommunication system (UMTS) and is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE.
Inter-cell Interference Coordination (ICIC) is an operation of managing radio resources so that control of inter-cell interference can be maintained. ICIC mechanism can be divided into frequency domain ICIC and time domain ICIC. ICIC includes multiple cell RRM (Radio Resource Management) function which requires considering of information from multiple cells.
Frequency domain ICIC coordinates the use of frequency domain resources (e.g., RB (resource block)) among multiple cells. Time domain ICIC coordinates time domain resources (e.g., subframes) among multiple cells.
In ICIC, interference the object causing interference (i.e., interfering cell) and the object inflicted by the interference (i.e., interfered cell) are determined depending on the object of measurement by the terminal
In many networks, depending on the methods of manipulating networks, downlink transmissions between the serving cell and neighbor cells are not exactly synchronized in time domain. However, in order for the serving cell to apply ICIC mechanism considering the interference which neighbor cells affect to the terminal, it is necessary to know exactly the difference between the downlink timing of neighbor cells and the downlink timing of the serving cell.
The downlink timing of the serving cell and neighbor cells experienced by the terminal can be different depending on the location of the terminal or surrounding environments.
Therefore, ICIC taking consideration of the difference in downlink timing of multiple cells is needed.